EVALUATION METHOD OF FORMATION RESISTIVITY AT INVESTIGATIONS OF WELLS CASED WITH METAL STRING Russian patent published in 2013 - IPC G01V3/20 G01V3/38 

FIELD: oil and gas industry.

SUBSTANCE: invention can be used during evaluation of current oil and gas saturation of a formation by applying the resistivity determining method. The above method involves determination of resistivity of the open shaft medium as per the lateral logging (LL) data using standard dependence, according to which and unlike known methods, lateral logging is performed after the open shaft of the well is filled with mineralised solution having the composition identical to the composition of drilling mud used at drilling of that well. Resistivity of casing string is accepted equal to such resistivity of drilling mud, at which evaluation of resistivity of dense rocks turns out to be equal to resistivity of those rocks as per the open well shaft data. Resistivity of the formation is calculated by adding the specified resistivity value of drilling mud to the following formula: where: p_k- apparent resistivity of the string as per LL-3, Ohm·m; p_c - drilling mud resistivity, Ohm·m; p_n - formation resistivity, Ohm·m; L - probe length, m; d - well diameter, mm; d₃ - probe diameter, mm.

EFFECT: improving the sounding data accuracy.

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